Knowledge of the basic kinetic parameters, bioavailability, dose proportional range, and internal dose are indispensable for dose selection in toxicology studies, interpretation of toxicology study results, facilitation of interspecies scaling and risk assessment. The toxicokinetic studies of benzyl acetate, naphthalene, and pyridine have been conducted in F344/N rats and B6C3F1 mice. Benzyl acetate, a flavoring agent, was shown to be carcinogenic in a study that used the gavage route of dosing but not in a study in which the chemical was added to the diet. To try to understand these conflicting results the internal dose was determined in rodents that were dosed by the two routes. A much higher exposure to the chemical was demonstrated in the gavage study than during the feeding study using similar dosages. The kinetics of naphthalene, a synthetic Intermediate and a moth repellent, has not been characterized. To assist in the design and subsequent interpretation of planned inhalation toxicology and toxicokinetic studies an analytical method was needed to quantitate the chemical in biological samples. A method was developed and validated for use in the planned studies. A carcinogenicity study of pyridine, a solvent and a synthetic intermediate, was conducted by the NTP. Subsequently, toxicokinetic studies were conducted to help interpret the results. Bioavailability was shown to be nearly 100% but the elimination processes were saturable. These finding should shed new light on the interpretation of the toxicology findings.